Gov. Jerry Brown’s ambitious tunnels designed to ship water partly underground to Southern California would be tall enough to comfortably fit an adult giraffe, wide enough for three freeway lanes and have ample room to carry enough water to serve 35,000 homes on a typical day.

But the barriers to Brown’s project may be even more immense. There is the $14 billion price tag. Powerful state and federal environmental regulators have to be convinced. History has not been an ally. And those whose lives could be upended are defiant.

“Yes, this is big. But so is the problem,” Brown said.

The two 35-mile-long tunnels would be laid out side-by-side, 150-feet under the Sacramento-San Joaquin Delta before connecting to an existing southbound aqueduct.

Construction and operational costs would be billed to those who stand to benefit the most: big users like the Metropolitan Water District, some cities near San Francisco and Central Valley irrigation districts that serve farmers.

Metropolitan has estimated ratepayers in San Diego County could see their bills go up by about $6 monthly and farmers, particularly avocado growers in North County, will also pay more.

The Brown administration has been methodically moving ahead with the “twin tunnels” project for some time, but a final design and environmental approvals are months away. A cost analysis is due April 22.

The forecast calls for a 2016 groundbreaking and 2026 ribbon-cutting.

Currently, powerful pumps push southbound water through the delta, a 1,100 maze of waterways and crop-rich islands. About two-thirds of the state’s drinking water flow through the region.

Supporters say the tunnels would not draw any more water from the north than what has been made available historically. The project proposes a more efficient and environmentally friendly way by transporting supplies to farms, homes and businesses south of the delta and in San Diego, they say.

Court orders to protect fish have interrupted water deliveries, forcing farmers to leave land unplanted and heightened uncertainly in industries that count on large volumes of water, such as Silicon Valley computer chip-makers and biotech companies in San Diego.

To overcome those problems, the project includes new diversion points with better screens that would be located in a safer position so that massive fish kills would become a thing of the past. The older pumps would still be used, but not nearly as much, Brown’s team says.

The new diversion also would be less at risk of earthquakes and flooding than many of the older levees scattered throughout the delta, they contend.

Critics say a new canal threatens to rob the delta of fresh water essential to the environment, farming and fishing. The project is also too expensive, they say, and offers no guarantees of surviving a catastrophic earthquake or other disasters.

The tunnels, along with accompanying habitat restoration initiatives, could also take farms out of production, slice through orchards and fields, and close access roads, they say.

The state should first conduct a thorough analysis of how much water can be safely exported, suggested Doug Hemly, sitting in his packing house office just a few yards away from the proposed project.